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|
--
-- LIMIT
-- Check the LIMIT/OFFSET feature of SELECT
--
SELECT ''::text AS two, unique1, unique2, stringu1
FROM onek WHERE unique1 > 50
ORDER BY unique1 LIMIT 2;
two | unique1 | unique2 | stringu1
-----+---------+---------+----------
| 51 | 76 | ZBAAAA
| 52 | 985 | ACAAAA
(2 rows)
SELECT ''::text AS five, unique1, unique2, stringu1
FROM onek WHERE unique1 > 60
ORDER BY unique1 LIMIT 5;
five | unique1 | unique2 | stringu1
------+---------+---------+----------
| 61 | 560 | JCAAAA
| 62 | 633 | KCAAAA
| 63 | 296 | LCAAAA
| 64 | 479 | MCAAAA
| 65 | 64 | NCAAAA
(5 rows)
SELECT ''::text AS two, unique1, unique2, stringu1
FROM onek WHERE unique1 > 60 AND unique1 < 63
ORDER BY unique1 LIMIT 5;
two | unique1 | unique2 | stringu1
-----+---------+---------+----------
| 61 | 560 | JCAAAA
| 62 | 633 | KCAAAA
(2 rows)
SELECT ''::text AS three, unique1, unique2, stringu1
FROM onek WHERE unique1 > 100
ORDER BY unique1 LIMIT 3 OFFSET 20;
three | unique1 | unique2 | stringu1
-------+---------+---------+----------
| 121 | 700 | REAAAA
| 122 | 519 | SEAAAA
| 123 | 777 | TEAAAA
(3 rows)
SELECT ''::text AS zero, unique1, unique2, stringu1
FROM onek WHERE unique1 < 50
ORDER BY unique1 DESC LIMIT 8 OFFSET 99;
zero | unique1 | unique2 | stringu1
------+---------+---------+----------
(0 rows)
SELECT ''::text AS eleven, unique1, unique2, stringu1
FROM onek WHERE unique1 < 50
ORDER BY unique1 DESC LIMIT 20 OFFSET 39;
eleven | unique1 | unique2 | stringu1
--------+---------+---------+----------
| 10 | 520 | KAAAAA
| 9 | 49 | JAAAAA
| 8 | 653 | IAAAAA
| 7 | 647 | HAAAAA
| 6 | 978 | GAAAAA
| 5 | 541 | FAAAAA
| 4 | 833 | EAAAAA
| 3 | 431 | DAAAAA
| 2 | 326 | CAAAAA
| 1 | 214 | BAAAAA
| 0 | 998 | AAAAAA
(11 rows)
SELECT ''::text AS ten, unique1, unique2, stringu1
FROM onek
ORDER BY unique1 OFFSET 990;
ten | unique1 | unique2 | stringu1
-----+---------+---------+----------
| 990 | 369 | CMAAAA
| 991 | 426 | DMAAAA
| 992 | 363 | EMAAAA
| 993 | 661 | FMAAAA
| 994 | 695 | GMAAAA
| 995 | 144 | HMAAAA
| 996 | 258 | IMAAAA
| 997 | 21 | JMAAAA
| 998 | 549 | KMAAAA
| 999 | 152 | LMAAAA
(10 rows)
SELECT ''::text AS five, unique1, unique2, stringu1
FROM onek
ORDER BY unique1 OFFSET 990 LIMIT 5;
five | unique1 | unique2 | stringu1
------+---------+---------+----------
| 990 | 369 | CMAAAA
| 991 | 426 | DMAAAA
| 992 | 363 | EMAAAA
| 993 | 661 | FMAAAA
| 994 | 695 | GMAAAA
(5 rows)
SELECT ''::text AS five, unique1, unique2, stringu1
FROM onek
ORDER BY unique1 LIMIT 5 OFFSET 900;
five | unique1 | unique2 | stringu1
------+---------+---------+----------
| 900 | 913 | QIAAAA
| 901 | 931 | RIAAAA
| 902 | 702 | SIAAAA
| 903 | 641 | TIAAAA
| 904 | 793 | UIAAAA
(5 rows)
-- Stress test for variable LIMIT in conjunction with bounded-heap sorting
SELECT
(SELECT n
FROM (VALUES (1)) AS x,
(SELECT n FROM generate_series(1,10) AS n
ORDER BY n LIMIT 1 OFFSET s-1) AS y) AS z
FROM generate_series(1,10) AS s;
z
----
1
2
3
4
5
6
7
8
9
10
(10 rows)
--
-- Test behavior of volatile and set-returning functions in conjunction
-- with ORDER BY and LIMIT.
--
create temp sequence testseq;
explain (verbose, costs off)
select unique1, unique2, nextval('testseq')
from tenk1 order by unique2 limit 10;
QUERY PLAN
----------------------------------------------------------------
Limit
Output: unique1, unique2, (nextval('testseq'::regclass))
-> Index Scan using tenk1_unique2 on public.tenk1
Output: unique1, unique2, nextval('testseq'::regclass)
(4 rows)
select unique1, unique2, nextval('testseq')
from tenk1 order by unique2 limit 10;
unique1 | unique2 | nextval
---------+---------+---------
8800 | 0 | 1
1891 | 1 | 2
3420 | 2 | 3
9850 | 3 | 4
7164 | 4 | 5
8009 | 5 | 6
5057 | 6 | 7
6701 | 7 | 8
4321 | 8 | 9
3043 | 9 | 10
(10 rows)
select currval('testseq');
currval
---------
10
(1 row)
explain (verbose, costs off)
select unique1, unique2, nextval('testseq')
from tenk1 order by tenthous limit 10;
QUERY PLAN
--------------------------------------------------------------------------
Limit
Output: unique1, unique2, (nextval('testseq'::regclass)), tenthous
-> Result
Output: unique1, unique2, nextval('testseq'::regclass), tenthous
-> Sort
Output: unique1, unique2, tenthous
Sort Key: tenk1.tenthous
-> Seq Scan on public.tenk1
Output: unique1, unique2, tenthous
(9 rows)
select unique1, unique2, nextval('testseq')
from tenk1 order by tenthous limit 10;
unique1 | unique2 | nextval
---------+---------+---------
0 | 9998 | 11
1 | 2838 | 12
2 | 2716 | 13
3 | 5679 | 14
4 | 1621 | 15
5 | 5557 | 16
6 | 2855 | 17
7 | 8518 | 18
8 | 5435 | 19
9 | 4463 | 20
(10 rows)
select currval('testseq');
currval
---------
20
(1 row)
explain (verbose, costs off)
select unique1, unique2, generate_series(1,10)
from tenk1 order by unique2 limit 7;
QUERY PLAN
----------------------------------------------------------
Limit
Output: unique1, unique2, (generate_series(1, 10))
-> Index Scan using tenk1_unique2 on public.tenk1
Output: unique1, unique2, generate_series(1, 10)
(4 rows)
select unique1, unique2, generate_series(1,10)
from tenk1 order by unique2 limit 7;
unique1 | unique2 | generate_series
---------+---------+-----------------
8800 | 0 | 1
8800 | 0 | 2
8800 | 0 | 3
8800 | 0 | 4
8800 | 0 | 5
8800 | 0 | 6
8800 | 0 | 7
(7 rows)
explain (verbose, costs off)
select unique1, unique2, generate_series(1,10)
from tenk1 order by tenthous limit 7;
QUERY PLAN
--------------------------------------------------------------------
Limit
Output: unique1, unique2, (generate_series(1, 10)), tenthous
-> Result
Output: unique1, unique2, generate_series(1, 10), tenthous
-> Sort
Output: unique1, unique2, tenthous
Sort Key: tenk1.tenthous
-> Seq Scan on public.tenk1
Output: unique1, unique2, tenthous
(9 rows)
select unique1, unique2, generate_series(1,10)
from tenk1 order by tenthous limit 7;
unique1 | unique2 | generate_series
---------+---------+-----------------
0 | 9998 | 1
0 | 9998 | 2
0 | 9998 | 3
0 | 9998 | 4
0 | 9998 | 5
0 | 9998 | 6
0 | 9998 | 7
(7 rows)
-- use of random() is to keep planner from folding the expressions together
explain (verbose, costs off)
select generate_series(0,2) as s1, generate_series((random()*.1)::int,2) as s2;
QUERY PLAN
------------------------------------------------------------------------------------------------------
Result
Output: generate_series(0, 2), generate_series(((random() * '0.1'::double precision))::integer, 2)
(2 rows)
select generate_series(0,2) as s1, generate_series((random()*.1)::int,2) as s2;
s1 | s2
----+----
0 | 0
1 | 1
2 | 2
(3 rows)
explain (verbose, costs off)
select generate_series(0,2) as s1, generate_series((random()*.1)::int,2) as s2
order by s2 desc;
QUERY PLAN
------------------------------------------------------------------------------------------------------------
Sort
Output: (generate_series(0, 2)), (generate_series(((random() * '0.1'::double precision))::integer, 2))
Sort Key: (generate_series(((random() * '0.1'::double precision))::integer, 2)) DESC
-> Result
Output: generate_series(0, 2), generate_series(((random() * '0.1'::double precision))::integer, 2)
(5 rows)
select generate_series(0,2) as s1, generate_series((random()*.1)::int,2) as s2
order by s2 desc;
s1 | s2
----+----
2 | 2
1 | 1
0 | 0
(3 rows)
-- test for failure to set all aggregates' aggtranstype
explain (verbose, costs off)
select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
from tenk1 group by thousand order by thousand limit 3;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------
Limit
Output: (sum(tenthous)), (((sum(tenthous))::double precision + (random() * '0'::double precision))), thousand
-> GroupAggregate
Output: sum(tenthous), ((sum(tenthous))::double precision + (random() * '0'::double precision)), thousand
Group Key: tenk1.thousand
-> Index Only Scan using tenk1_thous_tenthous on public.tenk1
Output: thousand, tenthous
(7 rows)
select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
from tenk1 group by thousand order by thousand limit 3;
s1 | s2
-------+-------
45000 | 45000
45010 | 45010
45020 | 45020
(3 rows)
|
